1. Field of the Invention
This invention relates to a retainer for releasably securing a punch within a bore of a punch ring, wherein the retainer is in the nature of a hand operable, elongated member that is selectively shiftable for releasing the punch from the ring.
2. Description of the Prior Art
Web fed printing presses commonly incorporate a punching system for forming a repetitive series of holes in the web as the latter is advanced. Typically, such punching systems have a spaced series of punches secured to a shaft-mounted punch ring and a mating die ring having a series of dies, wherein the die ring is secured to a second shaft in spaced, parallel disposition to the punch ring shaft. As the web is advanced toward the gap between the punch ring and the adjacent die ring, the punch ring and the die ring simultaneously counterrotate so that a piercing end of each punch registers with a respective die hole in the die ring and thereby simultaneously perforates the advancing web.
As is known, the piercing end of the individual punches is subject to wear, breakage and other damage during operation of the press such that replacement of the individual punches is required at relatively frequent intervals. As an example, such punches often last only about two weeks if the punching system is in continuous use. At the same time, the press might be provided with two or four 22" punch rings, wherein each of the rings carries forty-four punches. As can be appreciated, such a multitude of punches would desirably be secured to the punch ring in a manner such that removal and replacement can be accomplished within a short period of time.
In the past, various means have been proposed for releasably securing a punch to a punch ring or other support. One such method utilizes a set screw threaded through the punch ring that bears against the side of the punch. A related method is shown in U.S. Pat. No. 4,096,776 to Laucke, dated June 27, 1978, wherein a threaded pin retainer has a tapered section that is engageable with tapered grooves on a punch shank, and wherein a tool such as an allen wrench can be utilized for retractably rotating the pin retainer in order that the punch may be extracted from its support.
Other types of punch retaining devices are shown in U.S. Pat. No. 1,785,795 to Richard, dated Dec. 16, 1930 and U.S. Pat. No. 3,640,170 to Bennett, dated Feb. 8, 1972. Both of these references disclose the concept of a rotatable punch holding member having wall structure selectively engageable with a notch on a punch shank. By use of a wrench or lever, the punch holding member can be rotated to a position wherein the wall structure disengages the punch so that the latter may then be removed from the punch ring or other support.
Another type of punch retaining device is illustrated in U.S. Pat. No. 3,828,632 to Grano, dated Aug. 13, 1974, wherein is shown a spring loaded ball mounted within the punch ring and biased toward a peripheral groove of an adjacent punch shank. However, such structure is not entirely satisfactory since a tool must be utilized to grasp the punch head to exert a camming force on the ball against the compression of the spring so that the punch can be extracted from the punch ring. Moreover, dirt and metallic particles often accumulate in the area in the vicinity of the ball whereby movement of the latter and extraction of the punch is substantially hindered.
Thus, it would be a desirable advance in the art if means were devised to releasably secure a punch to a punch ring without the necessity of using tools or the like for removing the punch when necessary. Moreover, it is preferable that each of the individual punches can be separately removed without disturbing adjacent punches. In addition, such a retaining device must be operable to tightly secure the punch to the ring during operation of the press and withstand the outwardly directed force tending to pull the punch from the ring as the punch is withdrawn after the working stroke.